Considering a booster pump for a solar heater, I need advice

[longJohnGold]

Hey y'all! I just installed a solar heater pad but it's 70ft (23m) away (one way, not including the return back down) and has to climb a slope of 35 degrees, there's barely any water pressure.

My pump (3 hp) has to run at 2250 rpm just to move the water round trip.

My pool vac (suction side) barely moves.

I can't crank up the rpm (nor do I really want to) because the system pressure is about 12 PSI and the heaters are only rated for 10 PSI.

Post filter, I have a diverter to adjust how much water goes to the heater vs directly to the pool. The info above refers to 100% of the water going through the heater.

I'm trying to think of how I could make this work. Thinking a booster pump might solve the issue, but unsure of a couple of things:

1. Would a booster pump increase the overall system pressure? If so, significantly?
2. Where should it be placed? On the way up to the heater or on the way back down? Somewhere else?

Before installing the heater, I ran my pump at 1000 rpm for nearly 24 hours. It was super efficient, turning over 3+ times/day. But now with the heater requiring 2250rpm, yikes. The math figures that a booster pump will pay itself off in six-months time, tops.

I would love to get your thoughts folks, thanks for reading!

 

[mas985]

How high are the panels above the pump level?

35 degrees over 70 feet would imply about 50' rise which is extremely high. The pump needs to run at close to full speed for that rise.

Just because the filter pressure is 12 PSI, does not mean there is 12 PSI at the panels. Pressure drops with elevation. 50' rise is about 22 PSI drop in pressure so if the filter pressure is 32 PSI, the panels will be at less than 10 PSI.

But 10 PSI seems very low for solar panels. Most are in the range of 30 PSI. What is the make/model of the panels you are using?

 

[Darin]

Install a pressure gauge at your panes is the first data you need. Then go from there.

 

[Ahultin]

Hey y'all! I just installed a solar heater pad but it's 70ft (23m) away (one way, not including the return back down) and has to climb a slope of 35 degrees, there's barely any water pressure.

My pump (3 hp) has to run at 2250 rpm just to move the water round trip.

My pool vac (suction side) barely moves.

I can't crank up the rpm (nor do I really want to) because the system pressure is about 12 PSI and the heaters are only rated for 10 PSI.

Post filter, I have a diverter to adjust how much water goes to the heater vs directly to the pool. The info above refers to 100% of the water going through the heater.

I'm trying to think of how I could make this work. Thinking a booster pump might solve the issue, but unsure of a couple of things:

1. Would a booster pump increase the overall system pressure? If so, significantly?
2. Where should it be placed? On the way up to the heater or on the way back down? Somewhere else?

Before installing the heater, I ran my pump at 1000 rpm for nearly 24 hours. It was super efficient, turning over 3+ times/day. But now with the heater requiring 2250rpm, yikes. The math figures that a booster pump will pay itself off in six-months time, tops.

I would love to get your thoughts folks, thanks for reading!

I don't see any automation in your Signature line, do you have automation? Did you install a solar controller? We are in a similar climate And my solar with automation only runs a few hours per day , and even at that it cycles on and off several times per day. With automation you could set it up such that it closes the vacuum port while the solar is active and opens it when off. I have my pump set to the min speed to keep the swg happy (@1000rpm or 22gpm) when the solar is off. It then ramps up to 40gpm (@2300rpm) while solar is active.
Without automation you are potentially cooling the pool a good portion of the day.
I also second either installing a pressure guage at the panels or at least temporarily adding one to confirm actual pressure at the panels.

 

[1poolman1]

If you can find one, a single-speed .5 horsepower high-head pump, like a Whisperflow, that is fed water by the solar valve, should do what you are asking as long as the low speed of the main pump can keep it filled.

Remove plumbing after the solar valve and plumb to the inlet of the pump. Plumb the outlet of the pump to the the other pipe going to the solar. If your solar controller has the capability, it will actuate the pump along with the valve.

 

[longJohnGold]

Wow, many great responses and questions! This has already been so helpful.

How high are the panels above the pump level?

35 degrees over 70 feet would imply about 50' rise which is extremely high. The pump needs to run at close to full speed for that rise.

Just because the filter pressure is 12 PSI, does not mean there is 12 PSI at the panels. Pressure drops with elevation. 50' rise is about 22 PSI drop in pressure so if the filter pressure is 32 PSI, the panels will be at less than 10 PSI.

But 10 PSI seems very low for solar panels. Most are in the range of 30 PSI. What is the make/model of the panels you are using?

Panels are about 25' above the pump. The "35 degrees over 70 feet" involves ups and downs, so it's not a straight upward run. My bad on that, it wasn't a very accurate description. Just trying to say the water has an uphill battle. And actually, I might have some plumbing opportunities for efficiency with those "ups and downs" in the run. Will report back on that.

I don't know what I was thinking about the pressure . Thanks for clarifying the pressure will vary depending on the point in the system. Will definitely take @Darin 's advice and put a pressure gauge right at the panel entry point. This is certainly a key data point.

The panels are off-brand. Per the manufacturer:
Testing Pressure: 30 PSI
Working Pressure: 10 PSI

I think there is some play with the 10 PSI working pressure, but I don't want to push it too much.

 

[longJohnGold]

I don't see any automation in your Signature line, do you have automation? Did you install a solar controller? We are in a similar climate And my solar with automation only runs a few hours per day , and even at that it cycles on and off several times per day. With automation you could set it up such that it closes the vacuum port while the solar is active and opens it when off. I have my pump set to the min speed to keep the swg happy (@1000rpm or 22gpm) when the solar is off. It then ramps up to 40gpm (@2300rpm) while solar is active.
Without automation you are potentially cooling the pool a good portion of the day.
I also second either installing a pressure guage at the panels or at least temporarily adding one to confirm actual pressure at the panels.

No automation yet, just manually adjusting the diverter for now, but I will eventually be installing a controller and doing some automation. That's a neat setup you have btw.
Also, I just realized you're Bonsall, that's only 30 minutes away!

 

[longJohnGold]

If you can find one, a single-speed .5 horsepower high-head pump, like a Whisperflow, that is fed water by the solar valve, should do what you are asking as long as the low speed of the main pump can keep it filled.

Remove plumbing after the solar valve and plumb to the inlet of the pump. Plumb the outlet of the pump to the the other pipe going to the solar. If your solar controller has the capability, it will actuate the pump along with the valve.

Thanks for the recommendation on the pump. I didn't quite follow where you're saying to place the pump. I've marked where I think you're saying with a black "x" that has a red arrow pointing to it.

 

[1poolman1]

"X" marks the spot, despite what Indian Jones may have said.

 

[Dirk]

There are others already here that know more about this stuff than me, but I'll chime in anyway with some random thoughts, and they can correct me if I'm wrong.

25' up is like putting panels on a two-story house. Pretty sure that is well within the capability of a 3-HP pump without a booster. I don't see how running a booster, in addition to the main pump, in order to supply both the booster and panels with enough flow is going to be more cost-effective than just running the 3-HP at a higher RPM. @mas985 would likely know. But simpler is better. Pumping one pump through another, while done, adds an order of complexity that just doesn't sound worth it to me.

I have my panels on a one-story roof and run 2200RPM on a 3-HP pump, so you're not far off at all.

I don't attempt to run my pool vac and my solar at the same time, as they require different flow rates (RPM), so I just schedule them at different times. Problem solved. Filtering and chlorine generation (SWG) all happen at the flow rate the panels require, so there are no conflicts there.

You've got a handle now on the pressure at the panels, so no need to repeat, but it is not pressure you need to achieve (or safeguard), it is flow rate. All solar panels work best, in terms of heating efficiency vs pump energy required, at an optimum flow rate. That rate, ideally, is provided by the panel manufacturer. Mine, for example, is 5GPM (per panel). So that gets multiplied by the number of panels, eight in my case, so I need 40GPM to run my panels cost-effectively. That gives me close to the max of what my panels can produce in heat, without using more pump energy than I need to. I installed a FlowVis flow meter for that very purpose. Optimizing my panels was a very simple matter of adjusting my pump's RPMs until the FlowVis read 40. That's it. I don't worry about pressure, or elevation, or pump head, or anything else.

There are other ways to get there without a flow meter, but personally I didn't want to take the time to study and figure them out, when for about $100 I could buy a gizmo that gave me the exact solution, no math or guesswork involved. And I can adjust my RPMs throughout the season to accommodate a dirtying filter. I also use the FlowVis to monitor flow for my vac, and my SWG, too, so I got good value out of the purchase.*

The more important point is that you want to optimize the flow through the panels, by whatever means you can, and the rest is academic. And if that takes 2200RPM (or more or less), then so-be-it. If you want to heat your pool most efficiently, then that's what it's going to take. If you start trying to minimize RPMs, or adding a booster, or whatever, to try and save some money, I suspect you'll only be shooting yourself in the foot, when it comes to making your pool comfortable.

* If you're at all interested in a flow meter, the FlowVis is based on a Jandy check valve body. You can buy them two ways, with the body, or just the guts. If you already have a Jandy check valve in your plumbing, then you can just buy the FlowVis guts and bolt them to the existing Jandy body and save some money. A FlowVis is also a check valve, so it serves that purpose in addition to giving you flow rate.

 

[1poolman1]

There are others already here that know more about this stuff than me, but I'll chime in anyway with some random thoughts, and they can correct me if I'm wrong.

25' up is like putting panels on a two-story house. Pretty sure that is well within the capability of a 3-HP pump without a booster. I don't see how running a booster, in addition to the main pump, in order to supply both the booster and panels with enough flow is going to be more cost-effective than just running the 3-HP at a higher RPM. @mas985 would likely know. But simpler is better. Pumping one pump through another, while done, adds an order of complexity that just doesn't sound worth it to me.

I have my panels on a one-story roof and run 2200RPM on a 3-HP pump, so you're not far off at all.

I don't attempt to run my pool vac and my solar at the same time, as they require different flow rates (RPM), so I just schedule them at different times. Problem solved. Filtering and chlorine generation (SWG) all happen at the flow rate the panels require, so there are no conflicts there.

You've got a handle now on the pressure at the panels, so no need to repeat, but it is not pressure you need to achieve (or safeguard), it is flow rate. All solar panels work best, in terms of heating efficiency vs pump energy required, at an optimum flow rate. That rate, ideally, is provided by the panel manufacturer. Mine, for example, is 5GPM (per panel). So that gets multiplied by the number of panels, eight in my case, so I need 40GPM to run my panels cost-effectively. That gives me close to the max of what my panels can produce in heat, without using more pump energy than I need to. I installed a FlowVis flow meter for that very purpose. Optimizing my panels was a very simple matter of adjusting my pump's RPMs until the FlowVis read 40. That's it. I don't worry about pressure, or elevation, or pump head, or anything else.

There are other ways to get there without a flow meter, but personally I didn't want to take the time to study and figure them out, when for about $100 I could buy a gizmo that gave me the exact solution, no math or guesswork involved. And I can adjust my RPMs throughout the season to accommodate a dirtying filter. I also use the FlowVis to monitor flow for my vac, and my SWG, too, so I got good value out of the purchase.*

The more important point is that you want to optimize the flow through the panels, by whatever means you can, and the rest is academic. And if that takes 2200RPM (or more or less), then so-be-it. If you want to heat your pool most efficiently, then that's what it's going to take. If you start trying to minimize RPMs, or adding a booster, or whatever, to try and save some money, I suspect you'll only be shooting yourself in the foot, when it comes to making your pool comfortable.

* If you're at all interested in a flow meter, the FlowVis is based on a Jandy check valve body. You can buy them two ways, with the body, or just the guts. If you already have a Jandy check valve in your plumbing, then you can just buy the FlowVis guts and bolt them to the existing Jandy check and save some money. A FlowVis is also a check valve, so it serves that purpose in addition to giving you flow rate.

Very common, in my area, to see a solar booster pump installed as indicated, when the run to the solar panels is far and the roof high. It needs to be plumbed after the solar valve, not before, for the sake of the bearings (which is a long controversial subject).

In the foothills in my area there are some very large lots with the pools well below even the first-floor elevation of the home, which is almost always at least two stories. A half-horse booster works well on these installations, just very hard, if not impossible to find now.

There are stand-alone solar controllers that will operate both the valve and a booster pump as there is an application for them. Trying to run solar, filter, suction cleaner simultaneously has never worked well at any time, regardless the size of pump. Easy to arrange with automation, not so with just a dedicated solar control.

 

[mas985]

You definitely do not need a booster! It would increase energy use over the main pump alone with no real benefit.

25' is not very high even with a 70' run. My panels were 25' high and I used only a 1/2 HP pump (50' max head) so you really don't need much for panels. What matters is the rise and the maximum head of the pump. Both are well within the current pump's capability.

However, you do need to set the appropriate RPM for the given height of the panels. With 25' height, the minimum filter pressure needs to be at least 11 PSI at the filter just to get the flow rate started. You will want a flow rate of at least 0.1 GPM/sq-ft.

What is the total area of the panels?

Without the panels running, what is the filter pressure with the pump at full speed?

How far is the pump to the pool?

What size pipe is the suction line and is there more than one pool to pump?

What size pipe is used for the panels?

 

[Dirk]

You will want a flow rate of at least 0.1 GPM/sq-ft.

Yup, that jives with my panels' manufacturer's spec's. My panels are 12.5' x 4'. Times 0.1 = 5GPM. Times 8 panels = 40GPM total. Check.

And thanks for weighing in about the booster. With today's variable speed pumps, you just dial in what you need. They're very efficient compared to pumps just a few years ago. I just can't imagine how adding a second pump could use less electricity, even if you could dial back the VS pump some. And that's not even considering how much savings you'd have to achieve (even if you could) to pay for the second pump! The numbers just wouldn't add up.

And @1poolman1 confirms what I've already experienced myself. I just couldn't get my suction vac to perform well until I put it on its own. I have an actuated valve that draws about 80% of the suction from the vac. The other 20% I get from the skimmer, just as a safety precaution. When I tried to find a balance between vac and skimmer, so that I could run them both at the same time, neither worked well. Adding solar onto that would have just made it worse. Skimmer and solar work fine together. Vacuuming works best when nothing else is going on. Plus:

Something else to consider: a suction-side vac can be dangerous in two ways. The suction port in the pool, with a 3-HP pump, under the "right" conditions, can eviscerate a person. But so can the port in the vacuum head. That's why I run it only in the middle of night. No one is in the pool, and there's no solar pumping going on. It's also why I balance the vac's suction 80-20 with the skimmer's suction. It's still a risk, but if someone, somehow, got stuck to either vacuum port, there would still be flow through the skimmer, and hopefully not through that someone's body. Gross, I know, but something to be aware of when you plan your plumbing and your pump scheduling. They don't mention this stuff in the shiny vac brochures!!